import           Data.List     as List
import           Data.Map      as Map
import           Data.Maybe    as Maybe
import           Data.Sequence as Seq
import           Data.Set      as Set

maze = "#S######.#" ++
       "......#..#" ++
       ".#.##.##.#" ++
       ".#........" ++
       "##.##.####" ++
       "....#....#" ++
       ".#######.#" ++
       "....#....." ++
       ".####.####" ++
       "....#....G"

main = print $ fromMaybe 1000000 $ search m (Seq.fromList [(start, -1)]) Set.empty
  where coords = [(x,y) | x <- [1..10], y <- [1..10]]
        m = Map.fromList $ coords `List.zip` maze
        start = case List.elemIndex 'S' maze of Just i  -> coords !! i

type Coord = (Int, Int)

search ::  Map Coord Char -> Seq (Coord, Int) -> Set Coord -> Maybe Int
search m que visited = case Seq.viewl que of (c,d) :< que' -> search' c d que'
                                             _             -> Nothing
  where search' c@(x,y) d q = case Map.lookup c m of Nothing  -> search m q visited
                                                     Just '#' -> search m q visited
                                                     Just 'G' -> Just d
                                                     Just _   -> if Set.member c visited
                                                                 then search m q visited
                                                                 else let d' = d + 1
                                                                          q' = q |> ((x+1,y), d') |> ((x-1,y), d') |> ((x,y+1), d') |> ((x,y-1), d')
                                                                          visited' = Set.insert c visited
                                                                       in search m q' visited'